This invention is generally directed to developer compositions, and more specifically, the present invention relates to developer compositions with certain carriers. In embodiments of the present invention the carrier particles can be prepared by insitu processes and which carriers are comprised of a suitable core, such as a metallic core, or a metal oxide core, and preferably a hard magnetic porous metallic core or porous metal oxide core with a polymer contained in a number of the pores, that is for example from about 70 to about 90 percent of the pores, or all the pores that is about 100 percent of the pores, and wherein each of the pores is filled with polymer, for example from about 50 to about 100 percent, and preferably from about 90 to about 100 percent, and processes thereof. The carriers of the present invention may be mixed with toner of resin, colorant, and optional toner additives to provide developers that can be selected for the development of images in electrostatographic, especially xerographic imaging systems, and digital systems.
Insitu refers for example, to the polymerization being accomplished inside the carrier pores and at the surfaces of core particles; porous refers for example, to a foam-like structure, or a core that contains a plurality of pores. By hard magnetic is meant for example that the core comprises a hard magnetic material having a magnetic coercivity greater than about 200 for example about 300 to about 6,000 gauss.
Hard magnetic refers for example, generally to a core with permanent magnetic characteristics, that is the carrier possesses magnetic characteristics in the presence and in the absence of a magnet, and possesses a coercivity greater than about 200 gauss; and soft magnetic refers for example, to a carrier core that possesses magnetic characteristics in the present of a magnet and does not possess magnetic characteristics in the absence of a magnet.
The carrier, and the polymerization process to synthesize carrier of the present invention overcomes, or minimizes a number of disadvantages of the prior art. Furthermore, the polymerization process of the present invention enables the synthesis of hard magnetic carriers with wide ranges of triboelectric charging values, and various conductivities, and provides a small size carrier of for example, from about 25 to about 55 microns in volume average diameter as determined by a Coulter Counter. Further, when resin coated carrier particles are prepared by the polymerization, especially polymerization process of the present invention, the majority, that is, over 90 percent of the coating materials, such as polymer, or polymers are fused to the carrier surface thereby reducing the number of toner impaction sites on the carrier material. Additionally, there can be achieved with the carriers and processes of the present invention, independent of one another, desirable triboelectric charging characteristics and conductivity values; that is, for example the triboelectric charging parameter is not primarily dependent on the carrier coating weight as is believed to be the situation with the process of U.S. Pat. No. 4,233,387 wherein an increase in coating weight on the carrier particles may function to also permit an increase in the triboelectric charging characteristics. Specifically, therefore, with the carrier compositions and process of the present invention there can be formulated developers with selected triboelectric charging characteristics and/or conductivity values in a number of different combinations.